Rapid decline in 51Cr-EDTA measured renal function during the first weeks following lung transplantation

Chronic kidney disease after lung transplantation in a changing era

Lung transplant (LTx) physicians are responsible for highly complex post-LTx care, including monitoring of kidney function and responding to kidney function loss. Better survival of the LTx population and changing patient characteristics, including older age and increased comorbidity, result in growing numbers of LTx patients with chronic kidney disease (CKD). CKD after LTx is correlated with worse survival, decreased quality of life and high costs. Challenges lie in different aspects of post-LTx renal care. First, serum creatinine form the basis for estimating renal function, under the assumption that patients have stable muscle mass. Low or changes in muscle mass is frequent in the LTx population and may lead to misclassification of CKD. Second, standardizing post-LTx monitoring of kidney function and renal care might contribute to slow down CKD progression. Third, new treatment options for CKD risk factors, such as diabetes mellitus, proteinuria and heart failure, have entered clinical practice. These new treatments have not been studied in LTx yet but are of interest for future use. In this review we will address the difficult aspects of post-LTx renal care and evaluate new and promising future approaches to slow down CKD progression.

Estimating Renal Function Following Lung Transplantation

Background: Patients undergoing lung transplantation (LTx) experience a rapid decline in glomerular filtration rate (GFR) in the acute postoperative period. However, no prospective longitudinal studies directly comparing the performance of equations for estimating GFR in this patient population currently exist. Methods: In total, 32 patients undergoing LTx met the study criteria. At pre-LTx and 1-, 3-, and 12-weeks post-LTx, GFR was determined by ⁵¹Cr-EDTA and by equations for estimating GFR based on plasma (P)-Creatinine, P-Cystatin C, or a combination of both. Results: Measured GFR declined from 98.0 mL/min/1.73 m² at pre-LTx to 54.1 mL/min/1.73 m² at 12-weeks post-LTx. Equations based on P-Creatinine underestimated GFR decline after LTx, whereas equations based on P-Cystatin C overestimated this decline. Overall, the 2021 CKD-EPI combination equation had the lowest bias and highest precision at both pre-LTx and post-LTx. Conclusions: Caution must be applied when interpreting renal function based on equations for estimating GFR in the acute postoperative period following LTx. Simplified methods for measuring GFR may allow for more widespread use of measured GFR in this vulnerable patient population.

Assessment of kidney function: clinical indications for measured GFR

In the vast majority of cases, glomerular filtration rate (GFR) is estimated using serum creatinine, which is highly influenced by age, sex, muscle mass, body composition, severe chronic illness and many other factors. This often leads to misclassification of patients or potentially puts patients at risk for inappropriate clinical decisions. Possible solutions are the use of cystatin C as an alternative endogenous marker or performing direct measurement of GFR using an exogenous marker such as iohexol. The purpose of this review is to highlight clinical scenarios and conditions such as extreme body composition, Black race, disagreement between creatinine- and cystatin C-based estimated GFR (eGFR), drug dosing, liver cirrhosis, advanced chronic kidney disease and the transition to kidney replacement therapy, non-kidney solid organ transplant recipients and living kidney donors where creatinine-based GFR estimation may be invalid. In contrast to the majority of literature on measured GFR (mGFR), this review does not include aspects of mGFR for research or public health settings but aims to reach practicing clinicians and raise their understanding of the substantial limitations of creatinine. While including cystatin C as a renal biomarker in GFR estimating equations has been shown to increase the accuracy of the GFR estimate, there are also limitations to eGFR based on cystatin C alone or the combination of creatinine and cystatin C in the clinical scenarios described above that can be overcome by measuring GFR with an exogenous marker. We acknowledge that mGFR is not readily available in many centres but hope that this review will highlight and promote the expansion of kidney function diagnostics using standardized mGFR procedures as an important milestone towards more accurate and personalized medicine.

Rapid decline in 51Cr-ethylenediaminetetraacetic acid-measured renal function during the first weeks following liver transplantation

BACKGROUND

Renal dysfunction is a serious late complication after liver transplantation (LTX), but there are no studies addressing the early changes associated with this complication.

METHODS

We prospectively studied glomerular filtration rate (GFR) before and at 1, 3 and 12 weeks after LTX using 51Cr-labelled ethylenediaminetetraacetic acid clearance in 37 adult consecutive patients who underwent non-acute first LTX.

RESULTS

The mean (±SD) age was 49.5 ± 9.5 years, and the male:female sex ratio was 21:16. Diagnoses were autoimmune liver diseases (17), alcoholic cirrhosis (10) and other diseases (10). Immunosuppressive treatment consisted predominantly of triple-drug therapy. A total of 27 of the 37 patients were eligible for GFR analysis at all times. The mean (±SD) GFR was 86 ± 26 mL/min/1.73 m2 before LTX, and 77 ± 30 mL/min/1.73 m2 at 1 week, 64 ± 27 mL/min/1.73 m2 at 3 weeks and 64 ± 23 mL/min/1.73 m2 at 12 weeks after LTX, comparable to a reduction in mean GFR compared with baseline values of 10% (P = 0.1907), 25% (P = 0.0010) and 26% (P = 0.0007). Age and number of blood transfusions during surgery were identified as risk factors for this decline as well as gender, but not pre-transplant diagnosis, model of end-stage liver disease score, cold ischaemia time or post-transplant area under the curve tacrolimus during Days 0-14.

CONCLUSIONS

Using measured rather than estimated GFR, our results show that severe renal impairment occurs during the first week after LTX. These results emphasize the need for more studies addressing renoprotective treatment strategies.

Acute Kidney Injury after Lung Transplantation: A Systematic Review and Meta-Analysis

Background: Lung transplantation has been increasingly performed worldwide and is considered an effective therapy for patients with various causes of end-stage lung diseases. We performed a systematic review to assess the incidence and impact of acute kidney injury (AKI) and severe AKI requiring renal replacement therapy (RRT) in patients after lung transplantation. Methods: A literature search was conducted utilizing Ovid MEDLINE, EMBASE, and Cochrane Database from inception through June 2019. We included studies that evaluated the incidence of AKI, severe AKI requiring RRT, and mortality risk of AKI among patients after lung transplantation. Pooled incidence and odds ratios (ORs) with 95% confidence interval (CI) were obtained using random-effects meta-analysis. The protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42019134095). Results: A total of 26 cohort studies with a total of 40,592 patients after lung transplantation were enrolled. Overall, the pooled estimated incidence rates of AKI (by standard AKI definitions) and severe AKI requiring RRT following lung transplantation were 52.5% (95% CI: 45.8–59.1%) and 9.3% (95% CI: 7.6–11.4%). Meta-regression analysis demonstrated that the year of study did not significantly affect the incidence of AKI (p = 0.22) and severe AKI requiring RRT (p = 0.68). The pooled ORs of in-hospital mortality in patients after lung transplantation with AKI and severe AKI requiring RRT were 2.75 (95% CI, 1.18–6.41) and 10.89 (95% CI, 5.03–23.58). At five years, the pooled ORs of mortality among patients after lung transplantation with AKI and severe AKI requiring RRT were 1.47 (95% CI, 1.11–1.94) and 4.79 (95% CI, 3.58–6.40), respectively. Conclusion: The overall estimated incidence rates of AKI and severe AKI requiring RRT in patients after lung transplantation are 52.5% and 9.3%, respectively. Despite advances in therapy, the incidence of AKI in patients after lung transplantation does not seem to have decreased. In addition, AKI after lung transplantation is significantly associated with reduced short-term and long-term survival.

Renal function in pediatric cystic fibrosis patients in the first decade of life

With increasing life expectancy and the need for lung transplantation in the cystic fibrosis (CF) population, there are increasing reports of chronic kidney disease (CKD). However, values for baseline or longitudinal glomerular filtration rate (GFR) as measured by exogenous clearance markers are lacking in this population. Retrospective cross-sectional study in 2 to 18-year-olds cared for at a single CF center who had a GFR measured by plasma disappearance of Technetium-99 m diethylenetriaminepentaacetic acid (mGFR). The primary outcome was evidence of renal dysfunction as defined by CKD stage II or below (mGFR <90 ml/min/1.73 m(2), persistent abnormalities in urinary sediment, abnormal renal imaging). Of 63 patients evaluated, four had apparent renal dysfunction, one demonstrated decreased mGFR, and three others had persistent microscopic hematuria. The mean mGFR was substantially higher (140 ± 24 ml/min/1.73 m(2)) than expected or previously reported for healthy children. We did not demonstrate the presence of significant renal impairment after limited aminoglycoside exposure in the first decade following diagnosis with CF. However, we did document the presence of glomerular hyperfiltration in a significant proportion of our CF patients.

Cyclosporine C2 levels have impact on incidence of rejection in de novo lung but not heart transplant recipients: the NOCTURNE study

BACKGROUND

Cyclosporine (CsA) absorption varies early after transplantation and can be accurately assessed by the area under the absorption curve (AUC). The 2-hour post-dose (C2) level of CsA in whole blood is reported to be a useful surrogate marker of CsA AUC in kidney and liver transplant monitoring, but should be further explored in thoracic organ recipients.

METHODS

In a 12-month study we included de novo lung (n = 95) and heart (n = 96) recipients. All participants received cyclosporine (Sandimmun Neoral) monitored by C0 and blood was collected for analysis of C2 retrospectively. Abbreviated AUC (AUC(0-4)) was measured at 7 days and 3 months. Primary outcome was C2 relation to the frequency of acute cellular rejection (ACR) needing treatment and possible decline in measured glomerular filtration rate (mGFR). Recipients were divided into lower, middle and upper third C2 groups based on 2-week post-operative values (tertiles T1 to T3).

RESULTS

C2 was the most robust substitute for AUC(0-4) in the group of patients studied. For lung, but not heart, recipients there were differences in mean number of ACRs (p = 0.05), incidence of any rejections (p = 0.04), mean number of any rejections (p = 0.001) and time to first rejection (p = 0.03) between T1 and T3. C2 did not predict reduction in mGFR.

CONCLUSIONS

C2 is a sensitive predictor for ACR in lung, but not heart, recipients, C2 was not predictive of a decline in mGFR. This study suggests that management of lung recipients by C2 may diminish the number of ACRs.